Nanking Massacre, someone who knew a lot about CCP and KMT?

Okay, here's the problem. I am writing about Nanking Massacre. I wanted to talk about its possibility of being a political propaganda. If anyone could tell me the benefits of KMT or CCP exaggerating the Nanking Massacre for themselves, it would be greatly appreciated. I do not want something about modern perspective of Nanking Massacre. I want information regarding to why KMT or CCP would want to exaggerate the numbers. I will give out Life Savers pretty easily, give me something to go on. THANKS!~